I. Field of the Invention
This invention relates to a seat cushion to be used with a wheelchair, and more specifically to a seat cushion incorporating a shaped tray and an envelope filled with a flowable gel-like material.
II. Description of the Related Art
Users of wheelchairs typically have little or no use of their lower extremities. As such, they sit in wheelchairs, or similar structures such as recliners or beds, for long periods of time. Persons sitting in conventional wheelchairs or seats for long periods of time are sometimes prone to develop pressure sores, such as bed sores, at different points in the person's body which bear the weight of his body. For example, a person sitting upright in a wheelchair distributes his body weight over a relatively small area. As such, users of wheelchairs are prone to develop pressure sores.
In addressing this problem, related inventions have utilized envelopes filled with various cushioning media including air, elastomeric foams, and gels. In some embodiments, the gel has been mixed with lightening substance, such as hollow glass spheres, which tend to lighten the weight of the gel-filled envelope.
Some prior art designs have provided segments within the envelopes to improve the lateral stability to the user. For example, U.S. Pat. No. 4,588,229 to Jay discloses an envelope featuring a seam 39 separating the envelope into right and left hand portions. This seam prevents gel within the envelope from shifting from right to left within the envelope under the weight of the user, thereby enhancing the stability of the cushion. Also disclosed in U.S. Pat. No. 4,588,229 is a shaped tray designed to be used with the above-discussed envelope. The shaped tray is made of a lightweight material and has a depressed seat area 42 surrounded by rims 44, 46 on each side and a rim 48 in the front. The envelope is designed to be attached to the top surface of the tray and for them to be used as a unit.
The present invention contemplates a new and improved shaped tray which overcomes the foregoing difficulties and others while providing and more advantageous overall results.